1. Field
The present invention relates to an electronic apparatus having heat-generating components such as a semiconductor package and a chip set. Particularly, the invention relates to a structure that cools heat-generating components.
2. Description of the Related Art
A CPU is incorporated in, for example, notebook-type portable computers. The heat that the CPU generates while operating increases as its data-processing speed rises or as it performs more and more functions. The higher the temperature of the CPU, the less efficiently it operates. To cool the CPU, so-called “cooling system of liquid cooling type” have been developed in recent years. The cooling system uses a liquid coolant having a larger thermal conductivity constant than air.
Jpn. Pat. Appln. KOKAI Publication No. 7-142886 discloses a cooling system of liquid cooling type, configured for use in portable computers that comprises a main unit and a display unit. The cooling system comprises a heat-receiving header, heat-radiating header, and two tubes. The heat-receiving header is provided in the main unit and thermally connected to the CPU incorporated in the main unit. The heat-radiating header is provided in the display unit or in the main unit along with the heat-receiving header. If the heat-radiating header is provided in the display unit, the heat-radiating header lies adjacent to the display device incorporated in the display unit. Both tubes extend from the main unit to the display unit to circulate the liquid coolant between the heat-receiving header and the heat-radiating header.
In this cooling system, the liquid coolant absorbs the heat of the CPU in the heat-receiving header. In other words, the liquid coolant is heated in the heat-receiving header. The heated liquid coolant is supplied to the heat-radiating header via the first tube. As the coolant passes through the heat-radiating header, it releases the heat of the CPU. That is, the liquid coolant is cooled in the heat-radiating header. The cooled coolant is supplied back to the heat-receiving header via the second tube and absorbs the heat of the CPU. As the liquid coolant circulates, heat is transferred from the CPU to the heat-radiating header, which radiates the heat. Thus, the heat is released from the display unit or the main unit.
If the heat-radiating header that radiates the heat of the CPU is provided in the display unit, the heat-radiating header is adjacent to the display device incorporated in the display unit. The heat emanating from the heat-radiating header inevitably heats the display device. Consequently, the temperature of the display device may rise above the maximum use temperature. If this happens, the images that display device displays will be degraded in quality.
The heat-radiating header may be provided in the main unit. If this is the case, the heat emanating from the heat-radiating header accumulates in the main unit. When the temperature in the main unit rises, the circuit components and the disk drive, which are provided in the main unit, will be heated to high temperatures. The temperature of the circuit components, for example, may rise above their maximum thermal threshold. If this occurs, the circuit components may be degraded in performance or may undergo thermal breakdown.
U.S. Pat. No. 6,519,147 discloses a liquid-cooling system for use in portable computers having a body part and a display part. The cooling system comprises a heat-receiving head and a tube. The heat-receiving head is incorporated in the body part of the computer and connected to heat-generating components such as a CPU and a chip set. The tube is filled with liquid coolant and connected to the heat-receiving head. The tube extending between the body part and the display part.
The display part has a liquid crystal display panel and a housing containing the panel. The tube extends into the housing and lies in the gap between the liquid crystal display panel and the back of the housing. The tube meanders on the back of the housing, thus contacting the housing.
In this liquid-cooling system, the liquid coolant is heated as heat exchange is performed in the heat-receiving head. The liquid coolant heated flows in the tube toward the display part. As the liquid coolant flows through the tube, it transmits the heat of the heat-generating components to the housing. Therefore, the heat diffuses in the housing and is radiated from the entire back of the housing.
In the cooling systems, the liquid coolant heated in the heat-receiving header is led into the tube, raising the surface temperature of the tube. The tube is made of material having high heat-radiating property because it transmits the heat of the liquid coolant to the housing. The liquid crystal panel is liable to the heat emanating from the tube. When the panel is heated to high temperatures, the liquid crystal molecules cannot be oriented as is desired. In consequence, the images that the liquid crystal panel displays will be degraded in quality.